In industrial work areas, noise levels are sufficiently high that damage to the hearing of a worker may occur. The damage sometimes is very gradual, apparently being cumulative and sometime requiring years before the damage is noticeable. The damage occurs substantially without pain. As a consequence, many workmen gradually become deaf as a result of working in noisy environments. This deafness may be broad band across the entire audio spectrum. Other employees may lose substantial hearing at selected frequencies in the frequency range corresponding to the human voice.
Numerous earplugs have been devised in the past. It is believed that they have met with only limited success. The success has been primarily limited by the difficulty of fabrication. It is possible to make uniform or identically molded earplugs, but they do not uniformly fit the users. Users simply have different physical shapes, whether the earplug fits in the external ear or fits in some other fashion to the wearer and user. Mass produced uniformly made earplugs are generally not acceptable. To the extent that they are comfortable and fit well for some users, they are highly uncomfortable and fit very poorly with many other users. In this light, they will, in fact, either be ineffective or will be discarded if sufficiently discomforting.
The earplug of the present invention is a relatively simple device in retrospect. In this sense, it provides a radical change from the larger and cumbersome devices heretofore used. Moreover, it is a device that can be readily fitted to a large plant where scores, indeed hundreds, of workmen require individually fitted earplugs.
The present invention yields a product which is made from a cool impression of each ear of each individual user. Moreover, the attenuation may be adjusted to meet the noise level requirements of each user. The earplug which is made hereby has a substantially indefinite life and is not affected by the normal temperature excursions experienced by workmen. It typically does not require a coating or subsequent recoating as do some competitive devices. It is easily kept clean by daily washings with ordinary soap and water. Cleaning is easily achieved with boiling water. The device is believed to be substantially safer because it fits primarily in the ear canal only and not the outer ear. It can be attached by means of a long cord, exposed, and thus running from ear to ear so that supervisory personnel can readily observe a large work area with many workmen. This helps avoid discarding the ear protective devices which so many workmen do out of rebelliousness or resentment to the devices. The provision of a comfortable fit goes a long way in cutting down their resentment.
All of this is accomplished through the earplug of the present invention and the method for manufacturing disclosed herein.
The method of the present invention yields an improved earplug. This method results in the manufacture of an improved earplug. The earplug of the present invention is substantially improved in manufacturing over the earplug disclosed in the patent of Hocks, et al., U.S. Pat. No. 2,881,759. The device of Hocks is substantially worn in the external ear. The patent of French, U.S. Pat. No. 3,169,523, is directed to an external ear device. It is primarily on the exterior and is substantially exposed. The patent of Johnson, et al., U.S. Pat. No. 3,833,701, is substantially in the exterior ear. Moreover, the Johnson patent discloses a method of manufacture which is molded in situ. This is particularly set forth in multiple steps recited at Column 7 of that disclosure.
By contrast to these references, the method of the present invention yields a mass produced earplug which is substantially worn on the interior, not in the external ear.
The present apparatus and method for manufacturing yields an earplug which provides significant reduced sound levels in the critical frequency range of 1,000-8,000 Hertz. Reductions in the range of 30 db attenuation has been easily achieved with a vented version and more than 40 db attenuation with a nonvented version.
The present invention is a method of manufacturing which particularly lends itself to use in large plants where hundreds of employees must be individually measured and receive individually fabricated earplugs. By contrast, the present invention overcomes the shortcomings of the Johnson reference where attenuation is improved using a multiple number of dips (forming different or multiple layers) of a coated sealant placed on a base member. Johnson requires stretching of the external ear. It results in the fabrication of an earplug with an external handle which is not required. An external handle or projecting member is potentially dangerous from lateral impact to the head. The same exposure to lateral impact is found in the French reference.